Ion dynamic characterization using phase-resolved laser-induced fluorescence spectroscopy in a Hall effect thruster.

Area of Science:

• Plasma Physics
• Space Propulsion Engineering
• Advanced Diagnostic Techniques

Background:

• Hall effect thrusters (HETs) are crucial for space propulsion, but their plasma dynamics, especially during steady-state operation, exhibit time-dependent features.
• The breathing mode, characterized by discharge current oscillations, significantly impacts the ion velocity distribution function (IVDF), necessitating advanced diagnostic methods.
• Laser-induced fluorescence (LIF) is a minimally intrusive diagnostic technique offering high spatial resolution for IVDF measurements in HETs.

Purpose of the Study:

• To develop and present a novel phase-resolved LIF spectroscopy technique for studying plasma dynamics in HETs.
• To investigate the real-time modifications of the ion velocity distribution during the breathing mode oscillations.
• To enable simultaneous, phase-specific measurements of IVDF changes linked to discharge current fluctuations.

Main Methods:

• Utilizing laser-induced fluorescence (LIF) spectroscopy for plasma diagnostics.
• Applying the Hilbert transform to determine the instantaneous phase of the thruster discharge current oscillations (breathing mode).
• Implementing a fully numerical analysis for real-time, simultaneous measurement of IVDF modifications across different oscillation phases.

Main Results:

• Demonstrated a new method for phase-resolved LIF measurements in HETs.
• Successfully correlated instantaneous plasma properties with specific phases of the breathing mode oscillations.
• Provided real-time data on how ion velocity distributions evolve during cyclical discharge current variations.

Conclusions:

• The proposed phase-resolved LIF technique offers a powerful tool for understanding time-dependent plasma phenomena in HETs.
• This method allows for detailed analysis of the breathing mode's influence on ion dynamics.
• Future research can leverage this technique to optimize HET performance and stability.